This invention relates to a novel class of organotin compounds that are effective heat stabilizers for halogen-containing resins. This invention further relates to novel organotin compounds containing at least one sulfur atom that is bonded exclusively to tin or to tin and hydrogen. The compounds are derivatives of mercaptoalkanols, which are present as the free alcohols, as esters of polycarboxylic acids, esters of acids containing specified non-metallic elements or as alkoxides of specified metallic elements.
Organotin derivatives of mercaptoalkanols and mercaptoalkanol esters are disclosed in the prior art. U.S. Pat. No. 2,731,489 to Best teaches that organotin derivatives of mercaptoalkanol esters derived from monocarboxylic acids are effective stabilizers for vinyl chloride polymers. Kugele in U.S. Pat. No. 4,062,881 teaches that the performance of this type of stabilizer can be improved and the objectionable odor considerably reduced by introducing sulfide or polysulfide groups that are bonded exclusively to the same or different tin atoms.
It has now been found that the efficacy of many of the organotin stabilizers disclosed in the aforementioned Kugele and Best patents can be significantly increased if the hydroxyl group of the mercaptoalkanol is present as the free alcohol or is reacted to form (1) an ester of a polycarboxylic acid that is further esterified with at least one additional mercaptoalkanol group, (2) a derivative of a silicon-, phosphorus-, or boron-containing compound, or (3) an alkoxide of an aluminum- or titanium-containing compound.